1. Field of the Invention
The present invention relates to machine tools of the type having an intermittently revolving turret conveying a part or workpiece to be processed through a series of working stations in at least one of which there is provided a working cycle essentially longer than in the others.
Although the invention relates to machine tools of this type in a completely general way, reference is made hereinafter, for greater simplicity and clarity, to a coil winding machine, in which the application of the principles of the present invention proves to be particularly advantageous.
2. Brief Description of the Prior Art
In the field of coil winders or winding machines designed essentially to form windings for relays, or in any case windings with a medium-high number of turns, the idea of forming a plurality of windings at the same time so as to increase the productivity of the machine and reduce costs, is already known. For the practical carrying into effect of this idea, various types of machine have been proposed. These can be grouped essentially into three classes:
A. MACHINES WITH A SINGLE ROTATING SPINDLE ON WHICH A PLURALITY OF COIL SUPPORTS ARE PLACED AND WITH A SUBSTANTIALLY FIXED WIRE GUIDE. This type of machine, although it is very common, does not permit high outputs, nor does it allow automatic loading of the supports; moreover, it is generally employed for the windings only inasmuch as it does not lend itself to combination with apparatus for finishing the coils.
B. MACHINES EQUIPPED WITH A REVOLVING TABLE BY MEANS OF WHICH A PLURALITY OF WINDING HEADS EACH PROVIDED WITH A WINDING SPINDLE CARRYING A CORRESPONDING COIL SUPPORT ARE MOVED; THE ROTATING TABLE IS ADAPTED TO BRING EACH OF THE WINDING HEADS INTO CORRESPONDENCE WITH AT LEAST ONE FIXED STATION FOR LOADING, UNLOADING AND/OR FINISHING. In effect, these machines have a very high output, but they are also substantially more costly and generally require the constant attendance of an operator.
C. MACHINES WHICH MAKE USE OF AN INTERMITTENTLY ROTATING TURRET, ON WHICH THE COIL SUPPORTS ARE FIXEDLY MOUNTED, AND OF AT LEAST ONE FIXED WINDING HEAD WITH A ROTARY WIRE GUIDE AND WITH RESPECT TO WHICH THE INDEXING TURRET MOVES. This arrangement has the considerable advantage of allowing easy installation of complementary operative stations, such as, above all, a station for automatically loading the coil supports and, moreover, waxing, cutting, terminal bending and/or tinning and other stations, which will be referred to briefly hereinafter as finishing stations.
The present invention relates precisely to machines of the type indicated in paragraph c) and its object is principally to increase the productivity of these machines, essentially by reducing the waiting times, by extremely simple and effective means.
In effect, in machines of this type with an intermittently rotating turret, there is generally a considerable difference between the time necessary for winding a coil and the time necessary for executing the other operations of finishing; it happens, therefore, that at each cycle, all the finishing stations - their respective functions having been completed - remain inoperative throughout the additional time in which the winding operation is brought to an end. This fact therefore entails waiting or dead times at all the finishing stations and these have a negative effect on the productivity of the machine.
Various improvements have already been proposed for obviating this drawback:
A. According to one known improvement, use is made of a pair of winding heads disposed in diametrically opposite positions in relation to the rotating turret and after each of which respective finishing stations are provided. From the point of view of concept, this machine corresponds to a pair of single machines, so that with respect to the latter the advantages of high output, with lower total cost of the machine, is obtained; however, with this arrangement, the dead times at the finishing stations are exactly the same.
B. According to another improvement, the winding head is rendered capable of winding a series of coils, for example up to four coils, at the same time, and these are then generally treated simultaneously in the successive finishing stations. This is achieved principally by replacing the normal wire guide by a series of e.g. four, parallel wire guides which wind four coils simultaneously on four parallel fixed pins, for example as proposed in Italien Pat. No. 792,849 filed 27th Jan. 1967 by the same Applicant. This machine also does not eliminate the dead times in themselves, but it enables the loss due to the same to be distributed over a greater number of finished coils.
C. Following this last principle, it has also been proposed to dispose two or more coils coaxially on each fixed pin. This arrangement, however, has limits deriving: a) from the complication which would arise from the use of an automatic loading device, which would have to be adapted to pass two or more coil supports onto each spindle or pin at the same time; b) from the ratio between length and diameter of the pins, which, if they are not to be confined to the making only of very short coils, would generally have to be too high to permit the production of a sufficiently rigid and strong support; c) from the excessive extension which each wire guide would come to have, with the consequent risks of accentuated flexing and bending until the breaking point.